Any references to methods, apparatus or documents of the prior art are not to be taken as constituting any evidence or admission that they formed, or form part of the common general knowledge.
FIG. 1, depicts an earth moving machine 1. The earth moving machine 1 includes a dipper arm 3. A remote end of the dipper arm 3 is attached to a bucket attachment 5 by means of a quick coupler 7. The quick coupler 7 has a dipper side which mounts to the dipper arm 3 by means of first and second dipper coupling pins 9, 11. It also has an attachment side which includes jaws that engage first and second attachment coupling pins 13, 15. As is known in the prior art the locking of the quick coupler's jaws to at least one of the first and second attachment coupling pins 13, 15 is effected remotely from the cabin of the machine 1 by virtue of a hydraulic circuit that extends from controls in the cabin to one or more actuators of the coupler.
U.S. Pat. No. 6,964,122 describes a prior art quick coupler which includes a hydraulically operated moveable jaw that operates to capture the first attachment coupling pin and a latch mechanism that cooperates with a fixed jaw to capture the second attachment coupling pin. The quick coupler that is described in the '122 patent is explained to have the advantage of the latch continuing to retain the second attachment pin even if, due to a hydraulic circuit failure, the moveable jaw disengages from the first attachment coupling pin.
The quick coupler of the '122 patent and other similar quick couplers of the prior art manage to hold onto the bucket attachment by one pin in the event of a hydraulic failure. Consequently, the bucket attachment 5 does not fall from the dipper arm 3. Nevertheless the bucket attachment will swing rapidly and unexpectedly around the second attachment pin and may pose a serious threat of injury or even death to workers in the area.
It is an object of the present invention to provide an improved quick coupler which addresses or at least ameliorates the above described problem of the prior art.